The goal is to analyze human lymphoma and lymphocytic leukemias with hybridoma antibodies defining T-cell subsets in order to develop a comprehensive classification of human lymphomas based on the functional characteristics of the malignant cell and to provide an improved basis for treatment selection and prognostication. Suspensions prepared from lymph nodes involved by Hodgkin's disease and from a diverse group of lymph node hyperplasias were investigated with a panel of 10 monoclonal antibodies and a variety of conventional surface marker techniques. In both Hodgkin's disease and hyperplasia, 60% to 70% of the cells were T lymphocytes, approximately 80% of the inducer/helper subset and 20% of the cytotoxic/suppressor subset. The most prominent differences observed between Hodgkin's disease and hyperplastic T cells are explained by greater affinity of the sheep cell receptor on the surface of the lymphoma T lymphocytes. This greater affinity was best demonstrated by the formation of rosettes with unsensitized or immunoglobulin-sensitized sheep erythrocytes after incubation at 37~C, an occurrence observed only with Hodgkin's disease cells. In addition, in hyperplasia a variable proportion of lymphocytes reacting with the anti-T cell monoclonal antiserum OKT3 failed to form unsensitized rosettes at 4~C (E rosettes), while in Hodgkin's disease there are near equivalence of T cells that reacted with the antiserum and formed E rosettes. In addition to the increased affinity for sheep erythrocytes, some Hodgkin's disease specimens displayed increased reactivity with the monoclonal antibody OKM1, which reacts with monocytes and granulocytes, and the monoclonal antibody OKT10, which reacts with replicating lymphoid cells. Finally, 14 of 20 lymphoma samples exhibited polar migration of the fluorescent material (capping) with one or more antisera (most frequently OKI1, the monoclonal with specificity for the Ia-like antigen). These findings are useful in distinguishing Hodgkin's disease lymph nodes from hyperplasia by surface marker characteristics and may be relevant to older observations that Hodgkin's disease T cells aggregate about Reed-Sternberg cells. (2)